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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE. .\" SUCH DAMAGE.
.\" .\"
.\" @(#)vnconfig.8 8.1 (Berkeley) 6/5/93 .\" @(#)vnconfig.8 8.1 (Berkeley) 6/5/93
.\" from: src/usr.sbin/vnconfig/vnconfig.8,v 1.19 2000/12/27 15:30:29 .\" from: src/usr.sbin/vnconfig/vnconfig.8,v 1.19 2000/12/27 15:30:29
.\" .\"
.\" $FreeBSD$ .\" $FreeBSD$
.\" .\"
.Dd November 6, 2020 .Dd August 27, 2021
.Dt MDCONFIG 8 .Dt MDCONFIG 8
.Os .Os
.Sh NAME .Sh NAME
.Nm mdconfig .Nm mdconfig
.Nd create and control memory disks .Nd create and control memory disks
.Sh SYNOPSIS .Sh SYNOPSIS
.Nm .Nm
.Fl a .Fl a
▲ Show 20 Lines • Show All 192 Lines • ▼ Show 20 Lines
.It Oo Cm no Oc Ns Cm force .It Oo Cm no Oc Ns Cm force
Disable/enable extra sanity checks to prevent the user from doing something Disable/enable extra sanity checks to prevent the user from doing something
that might adversely affect the system. that might adversely affect the system.
This can be used with the This can be used with the
.Fl d .Fl d
flag to forcibly destroy an flag to forcibly destroy an
.Xr md 4 .Xr md 4
disk that is still in use. disk that is still in use.
.It Oo Cm no Oc Ns Cm mustdealloc
For
.Cm vnode
backed devices: detect whether hole-punching is supported by the underlying file
markjUnsubmitted
Done
Inline Actions
.Cm vnode
- backed devices: Detect if hole-punching is supported by the underlying file
+ backed devices: detect whether hole-punching is supported by the underlying file
system.
markj:
system.
If the file system supports hole-punching, then to handle a
markjUnsubmitted
Done
Inline Actions
system.
- If the file system supports hole-punching, for a
+ If the file system supports hole-punching, then to handle a
.Dv BIO_DELETE
markj:
.Dv BIO_DELETE
request, some or all of the request's operation range may be turned into a hole
markjUnsubmitted
Done
Inline Actions
.Dv BIO_DELETE
- request, a part of the request's operation range may be turned into a hole in
+ request, some or all of the request's operation range may be turned into a hole in
the file used for backing store.
markj:
in the file used for backing store.
Any parts which are not turned into holes are zero-filled in
the file.
If the file system does not support
markjUnsubmitted
Done
Inline Actions
the file.
- If the file system of the vnode type memory disk does not support
+ If the file system does not support
hole-punching,
markj:
hole-punching,
.Dv BIO_DELETE
requests to the device are not handled and will fail with
markjUnsubmitted
Done
Inline Actions
.Dv BIO_DELETE
- requests are returned unsupported.
+ requests to the device are not handled and will fail with
+ .Er EOPNOTSUPP .
.Pp
In case
markj:
.Er EOPNOTSUPP .
.Pp
markjUnsubmitted
Done
Inline Actions
requests are returned unsupported.
.Pp
- In case
+ When
.Cm mustdealloc
markj:
When
.Cm mustdealloc
is not specified or
.Oo Cm no Oc Ns Cm mustdealloc
is specified, for a
.Dv BIO_DELETE
markjUnsubmitted
Done
Inline Actions
.Dv BIO_DELETE
- request, if the file system supports hole-punching, a part of the request's
+ request, if the file system supports hole-punching, some or all of the request's
operation range may be turned into a hole in the file used for backing store.
markj:
request, if the file system supports hole-punching, some or all of the request's
operation range may be turned into a hole in the file used for backing store.
Any parts which are not turned into holes are zero-filled in the file.
If the file system of the vnode type memory disk does not support hole-punching,
the request's operation range is zero-filled in the file.
.It Oo Cm no Oc Ns Cm readonly .It Oo Cm no Oc Ns Cm readonly
Enable/disable readonly mode. Enable/disable readonly mode.
.It Oo Cm no Oc Ns Cm verify .It Oo Cm no Oc Ns Cm verify
For For
.Cm vnode .Cm vnode
backed devices: enable/disable requesting verification of the backed devices: enable/disable requesting verification of the
file used for backing store. file used for backing store.
The type of verification depends on which security features are available. The type of verification depends on which security features are available.
One example of verification is testing file integrity with One example of verification is testing file integrity with
checksums or cryptographic signatures. checksums or cryptographic signatures.
.El .El
.It Fl u Ar unit .It Fl u Ar unit
markjUnsubmitted
Not Done
Inline Actions

I think it could be a bit more clear:

  • Start the description with "For .Cm vnode backed devices:" like other vnode-specific option descriptions.
  • What happens if the file system does support hole-punching?
  • What happens when autounmap is not specified and BIO_DELETE is received?
  • Probably reference fspacectl.2 or just briefly describe the meaning of "hole-punching".

"autounmap" also seems like a somewhat strange name to me. Is it named after something similar elsewhere?

markj: I think it could be a bit more clear: - Start the description with "For .Cm vnode backed…
khngAuthorUnsubmitted
Not Done
Inline Actions

Do you think "mayunmap" is a better name?

khng: Do you think "mayunmap" is a better name?
markjUnsubmitted
Not Done
Inline Actions

Is "unmap" the usual terminology? fspacectl.2 refers to space deallocation, and we have _PC_DEALLOC_PRESENT, so maybe "mustdealloc"?

markj: Is "unmap" the usual terminology? fspacectl.2 refers to space deallocation, and we have…
Request a specific unit number or device name for the Request a specific unit number or device name for the
.Xr md 4 .Xr md 4
markjUnsubmitted
Done
Inline Actions
If the underlying file system of the vnode type memory disk does not support
- hole-punching, BIO_DELETE requests are returned unsupported.
+ hole-punching,
+ .Dv BIO_DELETE
+ requests are returned unsupported.
.El
.It Fl u Ar unit
markj:
device instead of automatic allocation. device instead of automatic allocation.
If a device name is specified, it must start with If a device name is specified, it must start with
.Dq md .Dq md
followed by the unit number. followed by the unit number.
.El .El
.Pp .Pp
The last form, The last form,
.Nm .Nm
▲ Show 20 Lines • Show All 63 Lines • ▼ Show 20 Lines
.Pa md1.nop .Pa md1.nop
to the start of the filesystem in the image. to the start of the filesystem in the image.
.Bd -literal -offset indent .Bd -literal -offset indent
mdconfig -u md1 -f diskimage.img mdconfig -u md1 -f diskimage.img
gnop create -o 512K md1 gnop create -o 512K md1
mount /dev/md1.nop /mnt mount /dev/md1.nop /mnt
.Ed .Ed
.Sh SEE ALSO .Sh SEE ALSO
.Xr fpathconf 2 ,
.Xr fspacectl 2 ,
.Xr open 2 , .Xr open 2 ,
.Xr md 4 , .Xr md 4 ,
.Xr ffs 7 , .Xr ffs 7 ,
.Xr gpart 8 , .Xr gpart 8 ,
.Xr mdmfs 8 , .Xr mdmfs 8 ,
.Xr malloc 9 .Xr malloc 9 ,
.Xr vn_deallocate 9
.Sh HISTORY .Sh HISTORY
The The
.Nm .Nm
utility first appeared in utility first appeared in
.Fx 5.0 .Fx 5.0
as a cleaner replacement for the vn kernel module as a cleaner replacement for the vn kernel module
and the vnconfig utility combo. and the vnconfig utility combo.
.Sh AUTHORS .Sh AUTHORS
The The
.Nm .Nm
utility was written by utility was written by
.An Poul-Henning Kamp Aq Mt phk@FreeBSD.org . .An Poul-Henning Kamp Aq Mt phk@FreeBSD.org .